1. Field of the Invention
The present invention relates to prosthetics and, more particularly, to a prosthetic socket adjustable test mounting system to allow convenient testing and adjustment of post-operative prosthetic devices for above-the-knee and below-the-knee amputation patients.
2. Description of the Background
There are a variety of different types of prosthetic devices for patients that have had either transfemoral (above-knee) or transtibial (below the knee) amputation. A typical modern prosthesis device consists of a custom socket fitted over the residual limb, a structural component system affixed to the socket that may include a pylon and articulated replacement joints (such as a knee or ankle) depending on the patient and location of the amputation, and knee cuffs, belts or other systems to secure the device to the body. A prosthetic sock or liner is typically worn over the residual limb within the socket to cushion the area of contact, and, in some cases, realistic-looking skin is provided over the structural components for aesthetic reasons.
One of the primary concerns of prosthesis design and construction is that the device be lightweight and provide a comfortable fit to the residual limb, and a natural gait when in use. As such, many of its components are made of high strength plastics such as polypropylene which is commonly used for socket construction and considerable effort is expended shaping the socket to conform the wearer. Lightweight metals such as titanium and aluminum have replaced much of the steel in the structural components. Some of the newest prostheses use carbon fiber to form a lightweight pylon and other elements. Certain other parts of the limb (for example, the feet) have traditionally been made of wood (such as maple or poplar) and rubber although modern feet are more commonly constructed with a wooden inner keel under urethane foam. Other materials commonly used are plastics such as polyethylene, polypropylene, acrylics, and polyurethane.
To provide the user with a comfortable and natural gait, it is of primary concern that the prosthesis be properly aligned so that its movement conforms to the shape and movement mechanics of the wearer's body. For example, a prosthetic knee joint provides a pivoting motion between upper leg and lower leg components and the plane defined by the pivoting movement may have to be fixed at a particular angle with respect to the wearer's sagittal plane to maximize the comfort and ease of use of the prosthetic device. Similarly, in a prosthesis for a transfemoral amputee, the foot may have to be disposed at a suitable angle relative to the direction of travel and the leg prosthesis may have to conform to a wearer's adduction or abduction contracture angles if such are indicated. To facilitate assembly of the device that conforms to the wearer's needs, the components of the device must be held in proper alignment while they are interconnected. The primary alignment criteria are height of the socket from the knee joint, and of the knee joint to the foot, articulating angle of the knee joint, the relative angle of the upper leg components (socket) versus the lower leg components (transfemoral prosthetic limb), the degree of rotational freedom about the knee joint, and lateral displacement (or offset) of the upper leg component from the lower leg component. These primary alignment criteria are typically derived quantitatively by trial fitting and adjustment of a test prosthesis on the wearer, which is then used to collect anatomical references for use in making the finished prosthetic components. Once a test prosthesis has been fully fitted and adjusted a prosthetist will commonly employ a specialized alignment transfer jig for measuring the primary alignment criteria. More specifically, the steps involved in properly aligning the prosthetic are detailed as follows:
The first step in the prosthesis fabrication process is a dynamic fitting process by which the prosthetist evaluates the amputee and makes a casting or digital reading of the residual limb or stump. From the cast a positive model of the stump is formed as a basis for creating the socket. The prosthetist may modify the positive model by adding or removing material to account for the location of bones and tendons in the residual limb and enhance comfort in weight-bearing areas. Where a digital impression has been taken such modification may be made within the computer model. When the prosthetist is satisfied by the initial model a thermoplastic such as clear polycarbonate is vacuum-formed over the positive form to create a test socket. Use of thermoplastics allows for reheating and localized modification of the shape during the fitting process.
Clear diagnostic test sockets are used in order to allow the prosthetist to see contact and pressure points between the socket and stump during actual use and weight bearing conditions. Using the clear diagnostic test socket, the prosthetist assembles an entire diagnostic prosthesis and spends considerable time working with the patient to adjust and modify the relative position of the structural components to achieve the desired fit and alignment as described. The structural elements (knee, pylon, ankle, foot etc.) of the diagnostic prosthesis, which may or may not ultimately be those used in the definitive prosthetic device, are affixed to the diagnostic test socket via a test mounting block for test fitting and adjustment in order to determine the optimal alignment prior to construction of the definitive prosthesis. The test mounting block is a puck-shaped disc. Once the optimal alignment is achieved the test measurement are transcribed or an alignment duplicating device (transfer jig) is used to transfer the alignment to a definitive prosthesis.
During fitting, the test mounting block is bonded to the underside of the clear diagnostic socket using epoxy or other adhesive such as polyurethane, and the mounting block/diagnostic socket junction is wrapped with casting tape to reinforce the joint. After the alignment process is completed, the alignment data is recorded (or marked directly onto the test socket and tape), the now-hardened casting tape is cut-off, and the mounting block is removed as it is no longer needed. The tape is typically removed by sawing it off which, given conventional test mounting blocks, often damages the block and inevitably destroys the block. For this reason, prosthetists have traditionally improvised their own test mounting blocks by fashioning single-use wooden, or in some cases aluminum, devices. The scarring imparted by the sawing tends to render the mounting block damaged, deformed and unusable (even aluminum test mounting blocks after just a few uses). It takes considerable time and expense to fabricate each test mounting block, and it would be greatly advantageous to provide one capable of use, easy recycling, and reuse for as many test mountings as desired.
It is noteworthy that there are a variety of prior art mounting blocks, but all are for permanent attachment of a prosthetic socket to the structural components and cannot easily be removed without damage. Further, most mounting means of the prior art require multiple components (sandwich) to properly function and are thus considerably complex.
For example, U.S. Pat. No. 5,545,230 to Kinsinger, et al. discloses provides an interface block which is attached to the stump socket and includes a movable nut which extends from the interface block. The prosthesis can be attached to the movable nut utilizing a bolt, such that the position of the prosthesis is clamped in place when the bolt is tightened. The amputee can test the prosthesis to ensure it is properly oriented and/or positioned and adjust the alignment by loosening the bolt. Once a desired alignment is achieved a resin is injected into a cavity of the interface block to maintain the relative position. The block is thus incorporated into the definitive prosthesis and not for use and reuse in a diagnostic prosthesis.
U.S. Pat. No. 6,458,163 to Slemker et al. discloses a base block subassembly is attachable to a first prosthetic limb component and a coupling-socket adapter rotatably attached to the base block subassembly and having a cavity for receiving a male coupling member (such as a boss of a pyramidal link-block). Various mechanisms, including a ring having internal threads and a ring-clamp, are disclosed for locking the coupling-socket adapter against rotation with respect to the base block subassembly and for unlocking the coupling-socket adapter for rotation with respect to the base block subassembly, wherein the mechanisms are operable when the base block subassembly is attached to the first prosthetic limb component. The device is again for use in a definitive device.
U.S. Pat. No. 6,123,732 to Gramnas discloses an adjustable adapter for lower leg prostheses including an adapter housing attachable to the lower leg prosthesis, a spheroidal adapter head rotatable inside the housing and a prosthesis collar attachment member that can be shifted sideways relative to the adapter head, which member can be fastened to a prosthesis collar whereby the spheroidal part of the adapter head is on the exterior of the essentially tube shaped adapter head having an internally tube shaped part in which there are parts arranged to allow the prosthesis collar attachment member to be shifted sideways.
U.S. Pat. No. 6,051,026 to Biedermann, discloses an alignment device for connecting a stump socket to a prosthetic limb having an alignment member with an opening receiving a pin connected to the stump socket. The size of the opening is considerably greater than the cross-sectional dimension of the pin and the pin can be locked in any position within the opening.
U.S. Pat. No. 5,047,063 to Chen discloses an adjustment device for artificial limbs includes a hollow cylindrical member having an open upper section and an open bottom end, and a block member disposed on and covering the open bottom end. A coupling member is received in the hollow cylindrical member and has a top block portion to cover a central through opening of the block member, and a downwardly extending post portion projecting from the top block portion and having a diameter smaller than the central through opening. The post portion extends through the central through opening of the block member. The hollow cylindrical member is laterally movable to adjust the position of the post portion in the central through opening. The post portion extends into a sleeve member. A mounting member has a cylindrical portion with an upper surface which is provided with a concave recess. The sleeve member is tiltably received in the concave recess so as to guide the post portion in an inclined position relative to a vertical axis of the mounting member. The lateral position of the post portion in the through opening and the inclination of the post portion relative to the vertical axis of the mounting member is adjusted to correspondingly adjust the center of gravity of an artificial limb incorporating the adjustment device to match the body equilibrium of a user.
U.S. Pat. No. 5,163,965 to Rasmusson et al. discloses an attachment device for joining endoskeletal prosthesis to prosthetic sockets. The couplers provide a flat mounting block having an annular ring or notch on their side surfaces which define a void into which thermoplastic material can be molded to effectively secure the coupler to the definitive socket. A depression is provided in the top surface of the device to facilitate fitting to a prosthetic socket. No means for removal of the block are provided.
U.S. Pat. No. 6,669,736 to Slemker discloses substantially flat and strong distal attachment block or base for the deposition of the fused-deposition-modeling materials in order to incorporate the block into a socket in a CAD enabled rapid prosthetic manufacturing process. attachment block may have a notch machined or formed into its proximal surface, about a periphery thereof, for receiving a first layer of the solidifying material and providing at least two bonding surfaces for the solidifying material. No means of removing the block from the socket are provided.
U.S. Pat. No. 5,545,231 to Houser discloses A system for adjusting the angle between a pylon and prosthetic foot in either or both of the medial/lateral plane or the anterior/posterior plane by placing at least one wedge between the pylon and the prosthetic foot. A barrel nut mounted in the lower end of a prosthetic pylon mates with a bolt extending from the prosthetic foot to secure the foot to the pylon. The angle of the barrel nut is adjusted in the anterior/posterior plane so that a threaded bore of the barrel nut is aligned with the bolt as its angle varies according to the angle of the wedge positioned between the pylon and prosthetic foot.
None of the foregoing references facilitate the test mounting process, and so it would be greatly advantageous to develop a diagnostic socket alignment system including an improved mounting block that is reusable and that facilitates mounting of the structural components to the test socket in order to construct and align the diagnostic prosthesis as well as convenient recycling of all components.